Anions in trade effluents - Determination of Anions in Natural and Treated Waters - page 588

10.4.5 Atomic absorption spectrometry
Jones [16] devised a procedure for determining cyanides whereby the cyanide is collected
on silver powder and cyanide determined on the silver by atomic absorption
spectrometry.
10.4.6 Polarography
Cyanide has been determined in industrial effluents by methods based on measurement of
the potential at −0.45V (vs SCE) in 0.01mol L −1 sodium hydroxide medium [17]. There
is no interference from phenol, acrylonitrile, urea or cyanide but sulphide and thiocyanate
interfere.
Square wave polarography has also been used to determine 1-100µg L −1 cyanide in
industrial effluents [18].
10.4.7 Ion selective electrodes
The application of cyanide selective electrodes has been discussed [19,20], Cuthbert [19]
used the technique to analyse steel works effluents. For cyanide concentrations above
1mg L −1 the electrode method and the standard argentimetric method gave similar
results; for lower cyanide concentrations, the colorimetric pyridine-pyrazolone method
gave higher results than either the potentiometric method or the colorimetric pyridine-
barbituric acid method. Cuthbert [19] discusses the problems associated with the
determination of cyanide in waste waters containing complex iron cyanides and
sulphides.
Hafton [21] used a silver ion selective electrode for the continuous determination of
free cyanide in effluents in concentrations of 0.01-1.0µg L −1 .
10.4.8 Microdiffusion
Rubio et al. [22] give details of a simple rapid procedure for the determination of cyanide
involving separation by microdiffusion followed by potentiometric determination in the
inner chamber of the microdiffusion cell. The limit of detection was 0.02µg L −1 cyanide.
10.4.9 Gas chromatography
Nota and Improta [23] determined cyanide in coke oven waste water by gas
chromatography. The method is based on treatment of the sample with bromine and
direct selective determination of the cyanogen bromide by gas-solid chromatography
using a BrCN selective detection as an electron capture detector. No preliminary
treatment of the sample to remove interferences is necessary in this method, and in this
sense, it has distinct advantages over many of the earlier procedures. Bromine also
oxidises thiocyanate to cyanogen bromide. Previous treatment of the sample with
aqueous formaldehyde destroys thiocyanate and prevents its interference in the method.
Nota et al. [24] have made the cyanogen bromide technique for determining cyanides